There exist numerous prior art designs for solar sensors, most of which are complex and expensive and have associated therewith electronic signal analysis systems that are bulky and comprise many minute parts. The complexity of these prior art designs makes them very difficult to manufacture and even more difficult to employ successfully in space-restricted environments such as the interiors of motor vehicles. Additionally, most prior art sensor designs cannot be calibrated to obtain an ideal angular response before leaving the factory, and therefore these designs require the use of complex correction circuitry.
Many prior art sensor designs employ a diffuser to modulate the angular response of a photodetector. For example, U.S. Pat. No. 4,632,542 to Whiteside discloses an exposure control system for use in a photographic camera wherein a diffuser may move into and out of the field of view of a photodetector. Additionally, U.S. Pat. No. 4,477,172 to Yokota discloses a light measuring device for a camera that includes a diffusion plate having three areas of different diffusion characteristics. The diffusion plate is stepwise movable so that one of the diffusion areas is axially aligned with the photodetector at any given time.
While such prior art devices provide desirable features, these desirable features still do not permit one to calibrate the angular response of a photodetector prior to installing the sensor in its end-use location. Therefore, these prior art devices must use complex and expensive electronic signal analysis systems and/or bulky and time-consuming manual movement mechanisms to provide the end user with the desired angular response from the photodetector.
There is therefore a need for a simple and inexpensive solar sensor that can determine the position of a source of incident solar radiation without requiring any special location computation or response correction processing system. That is, there exists a need for a solar sensor that can be calibrated initially to obtain a desired angular response and then fixed with that calibration for the life of the sensor. The present invention is directed toward meeting this need.